Field of the Invention
The present invention relates to an active mount which is mounted to a vehicle body to support an engine and changes damping characteristics depending on properties of transmitted vibration, and more particularly, to an active mount having a structure in which metallic scraps are mounted to a part portion, which constitutes a second lower liquid chamber, to suppress elastic deformation of the part portion using magnetic force in order to more precisely restrict behavior of the second lower liquid chamber.
Description of Related Art
An engine of a vehicle is installed in an engine room of a vehicle body by means of an (engine) mount in order to attenuate vibration in the engine. As the mount that is applied to a passenger vehicle, a rubber mount which insulates and attenuates vibration using elastic force of rubber, and a fluid filled type mount (hydraulic mount) in which a predetermined amount of a hydraulic liquid is encapsulated are generally and widely used.
Among the mounts, the fluid filled type mount has a structure in which a predetermined amount of hydraulic liquid is encapsulated therein and vibration is attenuated by a flow of the hydraulic liquid, and has an effect of simultaneously attenuating vibration in a high frequency region and a low frequency region, such that a range of application of the fluid filled type mount is gradually increased. Further, in order to more efficiently attenuate vibration in a certain frequency region by improving the fluid filled type mount, development of an active mount, which may actively control damping characteristics, is being conducted.
The active mount is configured to control dynamic characteristics of the mount in an On/Off manner. Further, in the case of the active mount, a volume-stiffness method, which controls behavior of a membrane that vibrates depending on a flow of the hydraulic liquid, and a by-pass method, which additionally forms a second flow path, which allows an upper liquid chamber and a lower liquid chamber to be in communication with each other, and restricts the communication of the second flow path, are widely used.
In general, in the case of a diesel engine vehicle, the by-pass method, which exhibits low properties (a dynamic ratio of about 0.6) in a low frequency region (20 to 40 Hz), is mainly used.
As illustrated in FIG. 1A and FIG. 1B, in an active mount according to the by-pass method in the related art, an insulator 140 made of elastic material is mounted at an upper side in a case, a diaphragm 101 is coupled at a low end of the case, and a nozzle plate 130 is mounted between the insulator 140 and the diaphragm 101, such that an internal space is divided into an upper liquid chamber and a lower liquid chamber. The nozzle plate 130 is configured so that an annular flow path 131 is formed in the nozzle plate 130 along a circumference of the nozzle plate 130 such that the encapsulated hydraulic liquid may flow between the upper liquid chamber 133 and the lower liquid chamber. The flow of the hydraulic liquid occurs as a volume in the upper liquid chamber is increased and decreased when the insulator 140 is elastically deformed by load movement and vibration transmitted from the engine.
A second flow path 132, which allows the upper liquid chamber 133 and the lower liquid chamber 103 to be additionally in communication with each other, is provided in the nozzle plate 130, and a body portion 104 having a cup shape presses an inflection portion of the diaphragm from a lower side of the inflection portion to divide the lower liquid chamber into a first lower liquid chamber 102 and a second lower liquid chamber 103. The first lower liquid chamber 102 is in communication with the upper liquid chamber 133 through the flow path 131, and the second lower liquid chamber 103 is in communication with the upper liquid chamber 133 through the second flow path 132.
A hole 105 is formed in a bottom surface of the body portion 104, and the hole 105 is opened and closed by a rod portion 108 which is moved upward and downward below the hole 105. When electric power is applied to the coil 106, the rod portion 108 is moved upward by electromagnetic force and closes the hole 105. When the hole 105 is closed, air is blocked from flowing to the interior of the body portion 104 (that is, a space between the body portion 104 and a part portion 101a), such that the part portion 101a, which is a portion of the diaphragm 101 positioned inside the body portion 104, is prevented from being elastically deformed, and as a result, a flow of the hydraulic liquid flowing through the second flow path 132 is restricted.
However, because the interior of the body portion 104 is not in a complete vacuum state (that is, because elastic behavior of the part portion is possible) even though the hole 105 is closed, there is a problem in that the hydraulic liquid minutely flows even through the second flow path 132.
That is, the structure of the related art has problems in that as the hydraulic liquid flows through the second flow path 132, a loss factor is decreased, and dynamic characteristics deteriorate.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.